COVID-19 linked to higher dementia risk in older adults, study finds

In a recent study posted to Preprints with The Lancet on the SSRN* server First Look, researchers investigated whether coronavirus disease 2019 (COVID-19) played a role in the development of new-onset dementia over different time intervals in adults above the age of 60 years.

*Important notice: Preprints with The Lancet / SSRN publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Background

Although the immediate concerns about the high morbidity and mortality rates associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been put to rest because of concerted efforts worldwide to vaccinate the global population, emerging evidence indicates that COVID-19 has long-term impacts on neurological trajectories. An increasing number of studies have been examining whether the pandemic has increased the risk of cognitive impairments or exacerbated neurodegenerative conditions such as dementia and Alzheimer’s disease.

Research indicates that older adults who have had SARS-CoV-2 infections are at a higher risk of cognitive decline as compared to matched healthy adults or individuals with other respiratory diseases. Neurobiological studies have also found that SARS-CoV-2 can trigger immune dysregulation, inflammation in the central nervous system, and autoimmune responses that can exacerbate and accelerate neurodegenerative conditions.

Furthermore, the increased levels of tau aggregation, deposition of amyloid-beta, tau, neurofilament light chain, and other cerebrospinal fluid markers associated with COVID-19 highlight the need to evaluate its role in triggering new-onset dementia.

About the study

In the present study, the researchers reviewed existing literature and conducted a meta-analysis to determine whether SARS-CoV-2 infections increase the risk of new-onset dementia in adults over the age of 60.

Despite growing evidence on the link between COVID-19 and the increased risk of exacerbation of neurodegenerative disorders such as dementia and Alzheimer’s disease, the findings on whether COVID-19 is associated with new-onset dementia remain inconclusive. The methodologies in the studies examining this association are highly variable across factors such as the baseline clinical data of the patients, durations of follow-up, study design, types of dementia examined, and demographic characteristics of the patients.

The meta-analysis aimed to analyze the findings from these varied studies to form a comprehensive understanding of the risk of new-onset dementia in older adults who have had SARS-CoV-2 infections and establish early intervention measures.

The review included studies that evaluated the long-term impact of SARS-CoV-2 infections in the onset of any form of dementia in adults over the age of 60 years who had survived COVID-19. Both retrospective and prospective observational studies that included patients who had recovered from COVID-19 and had undergone assessments for dementia were considered for the analysis.

Data extracted from the studies included the type of control groups used, the diagnosis method for detecting COVID-19, assessments used to diagnose dementia, type of dementia, the duration of the follow-up, and the type of respiratory infection, such as bacterial infection, influenza, or SARS-CoV-2.

Furthermore, the association between COVID-19 and the development of new-onset dementia was also analyzed for various subgroups based on sex, age groups, type of dementia, comorbidities, severity of SARS-CoV-2 infections, and follow-up durations. Types of dementia examined in the study included Alzheimer’s disease, all-cause dementia, Lewy body dementia, and vascular dementia.

Results

The results reported that SARS-CoV-2 infections might be associated with a higher risk of new-onset dementia in adults above the age of 60 years during the subacute or chronic phases of the infection after a COVID-19 diagnosis. However, the risk of new-onset dementia after COVID-19 did not seem to be higher than that after other respiratory infections, such as influenza or bacterial infections.

The researchers found that the risk of developing new-onset dementia after a SARS-CoV-2 infection was higher at the one-year follow-up compared to the three- and six-month follow-ups, suggesting that new-onset dementia was one of the long-term consequences of SARS-CoV-2 infections.

The subgroup analyses also indicated that irrespective of COVID-19 status, females were at a higher risk of developing Alzheimer’s disease and all-cause dementia than males. COVID-19 severity in older adults was also associated with an increased risk of new-onset dementia, although the definition of severe COVID-19 was found to vary across studies.

Conclusions

Overall, the findings suggested that compared to older adults who did not have SARS-CoV-2 infections, COVID-19 in adults above the age of 60 years was linked to a higher risk of new-onset dementia. However, the risk was found to be similar to that associated with respiratory infections from other etiological agents. Furthermore, the risk of new-onset dementia was found to be one of the long-term outcomes of COVID-19.

*Important notice: Preprints with The Lancet / SSRN publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.